1. Field of the Invention
The present invention relates generally to a push-to-talk (PTT) communication service in a portable terminal. More particularly, the present invention relates to an apparatus and method for determining a speaker in order to display the speaker's image while a PTT communication service is executed.
2. Description of the Related Art
Conventionally, a service area of a wireless communication system for portable terminals is divided into a plurality of base station (BS) areas, and includes cells serving as small-scale service areas. The BSs perform a central control operation by means of a mobile switching center (MSC), such that a subscriber can communicate with another party while moving between cells. With the development of communication technologies, various technologies for combining an Internet protocol (IP) network and a wireless communication network are being developed. One of the various technologies is called voice over IP (VoIP) for packet-based voice service using the IP.
Because conventional packet-based call service must establish a call through a mobile communication network and an IP network, there is a drawback in that a call setup time takes a long time. To overcome this drawback, a service for an interactive call such as a group or private call can be provided using a multicast function of the IP network. The interactive call is a communication call based on interaction between users. For example, the interactive call service has a push-to-talk (PTT) function similar to walkie-talkies. The term “group call” refers to communication between multiple users within a predefined user group. The term “private call” refers to 1:1 communication between users within a predefined user group. The PTT communication service can simultaneously provide voice/data services for a plurality of users or a group. The user informs a user device, that is, a portable terminal capable of using the PTT communication service that he or she wants to speak through the PTT communication service by pressing a PTT communication service button. The user device sends a service request to a network. The network rejects the request or assigns requested resources according to a predetermined determination criterion such as resource availability or a priority of the user making the request. At this time, the user is connected to other active users within a specific subscriber group. After a voice communication connection is established, the user making the request can transfer voice, and other users can listen to the transferred voice. When the user releases the PTT communication service, a corresponding portable terminal releasing the PTT communication service transmits a release message/signal to the network, such that the resources are released. A PTT communication system can perform a point-to-point or point-to-multipoint communication service.
The PTT communication service between PTT portable terminals is initiated when a PTT portable terminal at an origination side sends a PTT call request to a PTT portable terminal at a destination side. The PTT call request is enabled when a PTT button is pressed. The destination PTT portable terminal notifies the origination PTT portable terminal that the PTT call has been received. Then, the user of the destination PTT portable terminal recognizes a PTT notification sound, and initiates the PTT call with the user of the origination PTT portable terminal. At this time, a PTT communication subscriber (referred to as a “buddy”) gains the right to speak. Then, a buddy of the origination PTT portable terminal currently having the speaking right is indicated by a different color bar in a list of buddies displayed on the destination PTT portable terminal as illustrated in FIG. 5A. For example, when the PTT communication service is executed in a specific group of 10 buddies, all the 10 buddies cannot be displayed on one screen page. The 10 buddies must be displayed through multiple screen pages. Accordingly, after screen pages are shifted, the bar indicates a corresponding buddy having the speaking right. A conventional method for distinguishing and displaying a buddy having the speaking right has a drawback in that it is inconvenient for the user employing the PTT communication service to identify a buddy having the speaking right that is frequently shifted.
Because a corresponding buddy having the speaking right is indicated only by character data such as an identification (ID), the conventional PTT communication service cannot achieve a realistic visual effect.